Tool for fine machining boring surfaces

ABSTRACT

A cutter insert for a tool for the finish machining by chip removal of bore surfaces in workpieces is proposed, the cutter insert being inserted in a recess introduced into the peripheral surface of the tool and being held by means of at least one clamping shoe which interacts by means of a clamping lip with at least one clamping surface of the cutter insert, which is distinguished by the fact that the cutter insert, which preferably has a substantially rectangular configuration, has a hypothetical center line ( 39 ) with which the clamping surface ( 21; 21 ′) encloses an acute angle (α; α′).

DESCRIPTION

The invention relates to a cutter insert for a tool for the finishmachining, by chip removal, of bore surfaces in workpieces as describedin the preamble to claim 1 and relates to a tool as described in thepreamble to claim 9. The invention also relates to a cutter insert for atool for the chip-removal machining of bore surfaces as described in thepreamble to claim 10 and as described in the preamble to claim 16 and atool as described in the preamble to claim 17.

Cutter inserts and tools of the type discussed here are known. Thecutter insert(s) are held in the basic body of the tool with the aid ofat least one clamping shoe, a clamping lip of the clamping shoeinteracting with a clamping surface which is preferably arranged on theso-called cutter face, i.e. on the front surface of the cutter insert.It has been found that, particularly in the case of high machiningspeeds of 6000 rpm and more, secure retention of the cutter insert canno longer be ensured. This leads to people and machines in the vicinitybeing endangered because a cutter insert which is released can lead toinjury and/or damage.

It is therefore the object of the invention to create a cutter insertwhich can be securely fastened in an associated tool.

To achieve this object, a cutter insert is proposed which has thefeatures quoted in claim 1. The cutter insert is distinguished by thefact that it has a substantially rectangular configuration and that theclamping surface encloses an acute angle with the hypothetical centerline of the cutter insert. Because of this configuration, an obliqueclamping surface occurs which leads to secure retention of the cutterinsert in the tool.

An embodiment of the cutter insert is preferred which is characterizedin that the cutter insert is configured as a reversible insert and hastwo clamping surfaces of preferably identical configuration. Such acutter insert is characterized in that it can be rotated, in the case ofwear of one cutting edge, by 180° about an axis which is at right anglesto the center line so that a further cutting edge is available for thefinish machining of bore surfaces.

Further embodiments follow from the other sub-claims.

In order to achieve the object, a tool with the features of claim 9 is,in addition, proposed. It is distinguished by a high level of functionalsafety.

In order to achieve this object, a cutter insert with the features ofclaim 10 is also proposed. The cutter insert is characterized in thatthe clamping surface of the cutter insert is directed in such a waythat, when it is firmly clamped by means of the clamping shoe, thecutter insert permits the generation of clamping forces of which onecomponent acts against the centrifugal force and guarantees secureretention of the cutter insert in the basic body of the tool.

An embodiment example of the cutter insert is preferred which ischaracterized in that the clamping surface is arranged so as to beinclined in two directions relative to a hypothetical central plane ofthe cutter insert. On the one hand, this special arrangement of theclamping surface ensures build-up of the usual clamping forces, whichanchor the cutter insert in the basic body of the tool and press itagainst an abutment which absorbs the cutting forces occurring duringthe machining of bore surfaces. On the other hand, the inclination ofthe clamping surface in the second direction ensures that—asstated—clamping forces are built up which force the cutter insert in thedirection of the axis of rotation of the tool and therefore act againstthe centrifugal forces. In this way, it is possible to ensure—withoutparticular design complexity—that the cutter insert is secured againstdisplacement even at high rotational speeds.

Particularly preferred is an embodiment example of the cutter insertwhich is characterized in that the cutter insert is configured as areversible insert in which the clamping surface has two clamping surfaceregions which are arranged so as to be inclined in two directionsrelative to the hypothetical central plane of the cutter insert. The twoclamping surface regions intersect in an intersection line whichencloses an angle with a hypothetical center line of the cutter insert.Even in the case of a rotation by 180° about an axis at right angles toa front surface of the cutter insert, this ensures that a cutter insertof this type is both pressed against an abutment and subjected toclamping forces which are directed in the direction toward the axis ofrotation of the tool and secure the cutter insert against displacementat high centrifugal forces.

Further embodiments follow from the other sub-claims.

In order to achieve this object, a cutter insert with the features ofclaim 16 is also proposed which is characterized in that the clampingsurface is arranged in the region of a narrow side of the cutter insert.This clamping surface interacts with an abutment which is inclined insuch a way that, when the cutter insert is firmly clamped, clampingforces are built up which oppose the centrifugal force and securelyretain the cutter insert even at high rotational speeds.

In order to achieve the object, a tool is also proposed which has thefeatures quoted in claim 17.

The invention is explained in more detail below using the drawing. Inthis:

FIG. 1 shows a perspective view of a tool with a cutter insert,

FIG. 2 shows a perspective view of a cutter insert,

FIG. 3 shows a view onto the end surface of a cutter insert,

FIG. 4 shows a side view of a tool, shown as excerpt,

FIG. 5 shows a first embodiment example of a cutter insert of the toolshown in FIG. 4,

FIG. 6 shows a partial representation of the tool shown in FIG. 4,

FIG. 7 shows the cutter insert held by a clamping shoe, and

FIGS. 8 and 9 show further embodiment examples of the cutter insert.

The cutter insert described below is used particularly for the finishmachining of bore surfaces. It should, however, be expressly noted thatthis cutter insert can be generally employed in chip-removal tools whichare introduced in bores during the machining of workpieces rotating athigh speed in order to machine the associated bore surfaces.

The tool 1 shown in FIG. 1 is used for the finish machining of a boresurface in a workpiece. In operation, it is put into rotation andintroduced into the bore to be machined.

The tool 1 has a basic body 3 in whose peripheral surface 5 at least onecutter insert 7 is inserted. For this purpose, a groove 9 accommodatingthe cutter insert is introduced into the peripheral surface 5 and thisgroove 9 extends at right angles to the axis of rotation 11 of the tool1. The cutter insert 7 is retained by a clamping shoe 13 which isfastened in the basic body 3 of the tool 1 by means of a clamping screw15, which is here only indicated. From the sketch shown in FIG. 1, whichillustrates the principle, it may be seen that the clamping shoe 13 actsby means of a clamping lip 17 on the front surface or cutter face 19 ofthe cutter insert 7. The clamping lip 17 is in contact with a clampingsurface 21 which is introduced into the cutter face 19.

The basic body 3 of the tool 1 has the configuration of a circularcylinder and is connected to a drive or to a machining tool (not shownhere) by means of a shaft 23 (here shown truncated).

A recess or flat, which forms a chip-removal space 25, is introducedinto the peripheral surface 5 of the basic body 3.

Shown purely as an example, provision is made in the tool shown in FIG.1 for two guide strips 27 and 29 to be introduced into the peripheralsurface 5 of the basic body 3. These guide strips are configured aselongated metal strips extending substantially parallel to the axis ofrotation 11 and are introduced into suitable grooves 31 and 33 and arefastened there. Viewed in the direction of rotation indicated by anarrow 35, the first guide strip 27 runs behind (lags) the cutter insert7 by approximately 40° whereas the second guide strip 29 is arranged tobe diametrically opposite the cutter insert 7.

From the sketch in FIG. 1 showing the principle, it may be seen that theleading edge of the clamping lip 17 does not extend exactly at rightangles to the axis of rotation 11 but extends more or less in thedirection of the diagonal of the cutter insert 7, which here has arectangular configuration. The essential point is that the leading edgeof the clamping lip 17 encloses an acute angle with a hypotheticalstraight line at right angles to the axis of rotation 11 or with oneparallel to it.

FIG. 2 shows a perspective view of the cutter insert 7 to an increasedscale. The rear surface 37 of the cutter insert 7 opposite to the cutterface 19 can be seen in the view. The rear surface 37 extends parallel tothe cutter face 19. It may be clearly seen that two clamping surfaces 21and 21′ are introduced into the cutter face 19. A clamping lip of aclamping shoe (not shown here) comes to rest on these clamping surfaces21 and 21′ when the cutter insert 7 is clamped in the basic body of atool. It may also be seen that, starting from the cutter face 19, theclamping surfaces fall away at an acute angle α relative to the plane inwhich the cutter face 19 is located.

FIG. 2 shows clearly that the boundary between the two clamping surfaces21 and 21′ encloses an acute angle with a hypothetical center line 39 ofthe cutter insert. Because the angle of inclination α of the clampingsurface 21 has the opposite orientation to the angle of inclination α′of the clamping surface 21′, the result is two clamping surfaces whichfall away in opposite senses and are staggered relative to one another.They are separated from one another by a boundary line 41 which extendssubstantially diagonally over the cutter face.

FIG. 2 also shows clearly that a boundary edge 43 of the clampingsurface 21 and a boundary edge 43′ of the clamping surface 21′ extendparallel to the center line 39 but also parallel to the surface edges 45and 45′ (here shown by interrupted lines), the surface edges herecoinciding with the longitudinal edges of the cutter insert or formingthese edges.

The length of the clamping surfaces 21 and 21′ is somewhat less than theoverall length of the cutter insert. They are arranged in such a waythat they terminate at a distance from the end surfaces 47 and 47′. Aclamping lip, which is in contact with a clamping surface 21 or 21′, istherefore laterally protected from the penetration of chips or otherimpurities.

The clamping surfaces 21 and 21′ have—viewed in a view onto the cutterface 19—a substantially triangular configuration. They form aright-angled triangle and their hypotenuse approximately coincides withthe boundary line 41 and the longer leg of the right-angled triangleforms the boundary edge 43 or 43′. The shorter leg of the right-angledtriangle extends parallel to the end surfaces 47. The inclination of theclamping surfaces 21 and 21′ is selected in such a way that the deepestpart of the clamping surface, viewed in the direction of the center line39, is arranged to be close to the end surface 47 or 47′.

FIG. 3 shows a view onto the end surface 47 of the cutter insert 7. Fromthis, it may be seen that the cutter face 19 and the rear surface 37extend parallel to one another and that the side surfaces of the cutterinsert following on from the cutter face 19 and the rear surface formthe cutting edges 49 and 49′ of the cutter insert. Cutter inserts of thetype discussed here are fundamentally known so that they do not have tobe considered in any more detail here.

The representation in FIG. 3 shows that the clamping surfaces 21 and 21′fall away at the same angle relative to the plane in which the cutterface 19 is located but that the clamping surfaces fall away in oppositedirections relative to one another. For this reason, these clampingsurfaces are referred to as being staggered relative to one another.

As far as the function of the clamping surfaces 21 and 21′ is concerned,it is in the end unimportant whether these extend as far as the endsurfaces 47, 47′ of the cutter insert 7 or not. For reasons ofprotection from dirt, however, it is preferable that the length of theclamping surfaces should be chosen to be shorter than the overall lengthof the cutter insert.

The special arrangement of the cutter insert 7 and of its clampingsurfaces 21 and 21′ will be considered again in more detail inassociation with FIG. 1:

The cutter insert 7, configured here as a reversible plate as anexample, is arranged—as has been stated—in a groove 9 whose length ismatched to the length of the cutter insert. The end surface of thecutter insert facing away from the front surface 51 of the tool 1 istherefore located at the bottom of the groove 9. At the same time, theend surface of the cutter insert facing toward the axis of rotation 11is located at the end of the groove. Because the clamping surface 21 or21′ extends at an angle to the hypothetical center line 39, the cutterinsert is pressed —in the manner of a wedge mechanism and due to theclamping effect of the clamping lip 17 or the clamping shoe 13—againstthe radially inner end of the groove 9, on the one hand, and against thebottom of the groove facing away from the end surface 51, on the other.

From what is stated here, it is immediately clear that, on the basis ofthis double effect of the clamping shoe, the cutter insert 7 is retainedparticularly securely in the basic body 3 of the tool 1. This is,furthermore, also the case when the hypothetical center line 39 of thecutter insert 7 in a tool 1 extends parallel to the axis of rotation 11and the cutter insert is subjected to forces directed outward at rightangles to the axis of rotation 11 at a high rotational speed of thetool. It may, therefore, be seen that the clamping surfaces of thecutter insert are always arranged at an angle to the centrifugal forcesacting at right angles to the axis of rotation even in the case of anarrangement of the cutter insert in the basic body 3 of the tool 1 whichis displaced by 90°. There is, therefore, secure retention of the cutterinsert 7 in the groove 9.

It may be readily seen that the fact that the clamping surface extendsobliquely to the axis of rotation 11 is decisive for the secure clampingof the cutter insert 7 in the basic body 3 of a tool 1 so as to avoidaccidental release of the cutter insert at high rotational speeds of thetool 1.

The secure clamping of the cutter insert in a tool does not, in the end,depend on the basic shape of the cutter insert and on the number of theclamping surfaces. Cutter inserts other than rectangular reversibleinserts—for example hexagonal inserts—can therefore also be employedprovided the basic idea of the oblique arrangement of the clampingsurfaces relative to the axis of rotation 11 is preserved. It istherefore also obviously possible to introduce more than one cutterinsert into the basic body of a tool and, by this means, to provide anorientation of the cutter insert in which the hypothetical center line39 thereof extends substantially parallel to the axis of rotation 11 orsubstantially at right angles to the latter. In both assembly positions,this ensures that unintentional release of the cutter insert is avoidedwith a high degree of reliability because of the clamping surface whichextends at an angle to the axis of rotation 11. Attention is againexpressly drawn to the fact that cutter inserts with only one clampingsurface do exhibit the same advantages as reversible inserts with twoclamping surfaces.

The cutter insert described here is preferably manufactured by asintering process. It is, however, also possible to generate theclamping surfaces present in the cutter face by an erosion process.

FIG. 4 shows an excerpt from a cylindrical tool 101, namely the frontpart of a tool 101, in which a cutter insert 103 is here inserted insuch a way that its longitudinal edges extend horizontally and,therefore, substantially at right angles to an axis of rotation D of thetool 101 which coincides with the center line. The cutter insert 103 isarranged in a groove 104 introduced into the tool 103, which groove104—or its longitudinal axis—extends in the radial direction relative tothe axis of rotation D of the tool 101. It is retained by a clampingshoe 105 which is in contact with the front surface or cutter face 107of the cutter insert 103 by means of a clamping lip 109. The cutterinsert 103 has a clamping surface 111 which interacts with the clampinglip 109. The surface 108 of the clamping shoe 105 facing away from thecutter face 107 preferably finishes level with a boundary surface of achip space R. For this purpose, the clamping shoe 105 is arranged to belet into a recess 112 introduced into the tool 101, the contours ofwhich recess 112 being matched to the external shape of the clampingshoe 105 in such a way that the clamping shoe is retained in the tool101 as a form fit.

The cutter insert 103 is inserted in the basic body 113 of the tool 101in such a way that it protrudes beyond the radial peripheral surface115.

Two guide strips 117 and 119 are here inserted in the peripheral surface115 and of these, the first guide strip 117 runs behind (lags) thecutter insert 103 by approximately 40°—viewed in the direction ofrotation of the tool 101 indicated by an arrow 121. The second guidestrip 119 is inserted in the peripheral surface 115 diametricallyopposite to the cutter insert 103.

The basic structure of a reamer or of the tool 101 is known so that itwill not be considered in more detail here. With regard to the functionof the tool 101, the following is here recorded. The tool is inserted ina suitable retention feature, for example in a tool spindle, and is putinto rotation at high rotational speed. It is then inserted in a borewhose surface has to be machined. The bore surface is machined by thetool 101, or by the cutter insert 103 protruding beyond the peripheralsurface 115, by the removal of chips. The tool 101 is supported on thebore surface by means of the guide strips 117 and 119, the guide stripsthen also sliding on the surface. The chips removed by the cutter insert103 are removed via the chip space R which is formed by a recess in theperipheral surface 115. The chips can also be removed by a cooling andlubricating agent. The feed motion of the tool 101 is indicated by adouble arrow 125.

The cutter insert 103 is securely retained in the basic body 113 of thetool 101 by the clamping shoe 105. A clamping screw 127 is inserted toanchor the clamping shoe 105. It is also possible to use a plurality ofclamping shoes, in particular where the length of the cutter insert,measured in the radial direction, is larger.

The retention forces necessary to anchor the cutter insert 103 aregenerated in that the rear surface, opposite to the cutter face 107, ofthe cutter insert 103 is pressed against a contact surface of the tool101, so that frictional forces act. The cutting forces acting during themachining of a bore surface are taken up by an abutment 129 with whichthe side edge of the cutter insert 103 facing away from an end surface131 of the tool 101 is in contact. The leading side edge 133, viewed inthe feed direction, forms the active cutting edge of the cutter insert103. The active cutting edge protrudes beyond the end surface 131 sothat it can machine the bottom surface of blind holes.

The centrifugal forces arising at high rotational speeds and which couldlead to loosening of the cutter insert 103 are dealt with in that theclamping surface 111 is directed in such a way that, when the cutterinsert 103 is firmly clamped by means of the clamping shoe 105, clampingforces are built up of which one component acts against the centrifugalforce, i.e. at right angles to the axis of rotation D, so that thecutter insert 103 is forced in the direction toward the axis of rotationD.

FIG. 4 shows a tool 101 with a cutter insert 103 which is configured asa reversible insert.

Various embodiment possibilities of the tool or of the cutter insert areshown in FIGS. 5, 8 and 9.

FIG. 5 shows, in perspective representation, a cutter insert 103 such asis inserted in the tool 101 in FIG. 4 and which is configured as areversible insert. In the representation shown in FIG. 5, it is assumedthat in the case of the cutter insert 103, which is preferablyconfigured as a straight prism with a substantially hexagonal basesurface, the active cutting edge 137 is top left, which cutting edge 137has a main cutting edge and an auxiliary cutting edge, as is likewisethe case in conventional tools. It is not therefore considered in anymore detail here.

The clamping surface 111 can be seen here in the region of the cutterface 107—which is facing away from the observer in FIG. 5. The clampingsurface 111 has two clamping surface regions 139 and 141.

It is known art to equip cutter inserts with two clamping surfaceregions, namely when the cutter insert is configured as a reversibleinsert. In these known cutter inserts, the clamping surface isconfigured as a V-shaped groove, the two clamping surface regionsextending parallel to the longitudinal or side edges each falling away,viewed from the side edges, toward the hypothetical center line of thecutter insert so that, in this case, the intersection line of the twoclamping surface regions is the deepest region of the clamping surface.In addition, the intersection line extends parallel to the center lineof the cutter insert. In the known cutter inserts, therefore, theclamping surface regions intersect in an intersection line which extendsparallel to the center line.

In the tool 101 or the cutter insert 103 shown here, the intersectionline 145—which is formed by the two mutually intersecting clampingsurface regions 139 and 141—extends at an angle to the center line 143.The intersection line 145 here extends diagonally through the clampingsurface 111.

The cutter insert 103 shown here is characterized in that two clampingsurface regions 139 and 141 are provided in the region of the clampingsurface 111. These clamping surface regions 139 and 141 intersect in theregion of the intersection line 145 which forms the highest region ofthe clamping surface 111. The clamping surfaces 139, 141 fall away fromthe intersection line in the direction toward the side edges 133, 133′.In addition, the clamping surface region 139—in FIG. 5—falls away fromthe bottom toward the top whereas the clamping surface region 141 isinclined in the opposite sense and—in FIG. 5—falls away from the toptoward the bottom. In other words, the clamping surface regions 139 and141 are additionally inclined laterally. The left-hand clamping surfaceregion 139 falls away from the intersection line 145 to the upper outeredge 147. Correspondingly, the right-hand clamping surface region 141 inFIG. 5 falls away, starting from the intersection line 145, toward thelower outer edge 147′.

If a central plane of the cutter insert 103 extending parallel to theplane of the diagram of the representation in FIG. 5 is considered, theclamping surface regions 139 and 141 fall away relative to this centralplane in two directions or they are inclined in two directions relativeto the central plane. They therefore rise, on the one hand, toward thehypothetical center line 143 or toward the intersection line 145 and, onthe other hand, the left-hand clamping surface region 139 falls awayfrom the bottom toward the top whereas the right-hand clamping surfaceregion 141 falls away from the top toward the bottom. This meansthat—viewed in plan view—the depth of the clamping surface regions 139and 141—viewed in the longitudinal extent of the cutter insert103—changes.

If the clamping lip 109 of a clamping shoe 105 now engages on theleft-hand clamping surface region 139 of the clamping surface 111, aforce component arises which acts in the direction of the side edge133′, by means of which the cutter insert 103 is in contact with theabutment 129, as is shown in FIG. 4. The cutter insert 103 is thereforepressed against the abutment 129. At the same time, a force componentwhich acts downward—in FIG. 5—occurs because the clamping surface region139 falls away from the intersection line 145 toward the outer edge 147.In the representation of FIG. 4, this force component acts in thedirection of the axis of rotation D and ensures that the cutter insert103 is not displaced radially outward even in the case of highrotational speeds.

The left-hand—in FIG. 5—clamping surface region 139 widens—viewed fromthe side edge 133—toward the intersection line 145 and the right-handclamping surface region 141 becomes correspondingly narrower—viewed fromthe side edge 133′—in the direction toward the intersection line 145. Itis clear that the clamping surface does not extend to the side edges 133or 133′. Chip surfaces S and S′ follow directly from the side edges andchips removed from the cutting edges 137 and 137′ slide along these chipsurfaces S and S′.

In the embodiment example shown here, a narrow horizontal strip, whichseparates the clamping surface regions 139 and 141, is provided in theregion of the intersection line 145. It is also possible to provide suchstrips in the region of each of the left-hand and right-hand boundaryedges B and B′, the surface of these strips extending parallel orinclined to the plane of the diagram of FIG. 5 or to a hypotheticalcentral plane of the cutter insert 103.

The tool 101 reproduced in FIG. 4 is represented as an excerpt in FIG.6, the guide strips 117 and 119 not being shown to improvecomprehension. Otherwise, the same parts as those in FIG. 4 are providedwith the same reference designations, to this extent reference is madeto their Ad description. In addition, the clamping shoe 105 is onlyrepresented by a chain-dotted line, the clamping screw 127 beingomitted. In FIG. 6 it is clear that the cutter insert 103 is introducedinto the basic body 113 in such a way that its cutting edge 137protrudes beyond the radially extending peripheral surface 115. Theclamping surface 111 faces toward the observer—in contrast to therepresentation of FIG. 5. The clamping surface regions 139 and 141 aretherefore facing toward the clamping shoe 105, the clamping lip 109 ofthe clamping shoe 105 only subjecting the clamping surface region 139 toa force. Because the clamping surface region 139—in FIG. 6—falls awayfrom right to left, a force component which—in FIG. 6—forces the cutterinsert 103 in the direction toward the axis of rotation D, i.e. radiallyinward, occurs due to the application of force by the clamping shoe orclamping lip.

It may readily be seen from FIG. 6 that in the case of a rotation of thecutter insert 103, the surface of a bore can be machined by the activecutting edge 137′. The clamping surface region 141 is—in the position ofthe cutter insert 103 shown in FIG. 6—not touched by the clamping shoe105.

The tool 101 is shown as excerpt—viewed in the direction of the arrow IVin FIG. 6—in FIG. 7. The basic body 113 of the tool 101 is shownsectioned. Otherwise, the same parts as those in FIG. 4 to 6 areprovided with the same reference designations so that reference can bemade to their description.

FIG. 7 shows the clamping shoe 105 which is arranged in the recess 112of the basic body 113 in such a way that its surface 108 coincides witha surface 146 of the chip space R. The clamping shoe 105, which exerts aforce on the cutter insert 103, is anchored in the basic body 113 of thetool 101 by the clamping screw 127, the threaded hole in the basic body113 not being shown. The clamping lip 109 of the clamping shoe 105 isconfigured in such a way that its surface facing toward the clampingsurface 111 of the cutter insert 103 fits into the contour of theclamping surface region 139 or 141. Also shown is the groove 104 whichaccommodates the cutter insert 103. The groove 104 is configured in sucha way that it accommodates the cutter insert 103, which is essentiallyconfigured as a straight prism with a substantially hexagonal basesurface (FIG. 5). This means that the groove 104 represents an abutmentfor lateral boundary surfaces 153 and 155 of the cutter insert 103.

FIG. 8 shows a modified embodiment example of a tool 101 or a cutterface 107, here shown diagrammatically, of a cutter insert 103 which ischaracterized in that the clamping surface 111 is surrounded on allsides by a boundary surface 149 which extends substantially parallel tothe plane of representation in FIG. 8. Here again, the clamping surfaceregions 139 and 141 are separated by the intersection line 145 whichhere likewise forms a flat strip 151. In the embodiment example shownhere, the boundary surfaces 149 and the strip 151 are arranged in oneplane.

The essential feature is that the clamping surface regions 139 and 141are closed off on all sides so that a clamping lip 109 of a clampingshoe 105 is in contact in a protecting manner on the clamping surfaceregions and chips cannot pass under the clamping lip 109. By this means,the cutter insert 103 has a secure retention.

Otherwise, the same parts as the cutter insert represented in FIG. 6,which agree with those in the other FIGS. 4 to 7 are provided with thesame reference designations so that, to this extent, reference is madeto their description.

The cutter insert 103′ shown in FIG. 9 is modified to the extent thatone clamping surface 111′ is provided which extends at an acute anglerelative to the hypothetical center line 143 of the cutter insert 103′,the distance between the right-hand side edge 133′ and the center line143 increasing from top to bottom. In the case of such a cutter insert103, the abutment 129 (FIG. 4) is correspondingly inclined. This leadsto the fact that when the cutter insert 103′ is firmly clamped by meansof a clamping shoe 105, clamping forces are built up on the basis of theconfiguration of the clamping surface 111′ alone, which clamping forceshave at least one force component which acts from top to bottom in FIG.9 and force the cutter insert 103′ toward the axis of rotation D of thetool 101. The clamping surface 111′ is therefore configured in such away that a force component acts against the centrifugal force.

In the cutter insert 103′ of FIG. 9, a clamping shoe 105 likewiseengages on the clamping surface 111. Starting from the left-handboundary edge B of the clamping surface, the clamping surface canincrease as far as the right-hand boundary edge B′ of the clampingsurface 111. It is, however, also conceivable to configure the cutterinsert 103′ as a parallelogram and to use it as a reversible insert, theleft-hand side edge 133 extending in each case at an angle to the centerline 143 so that, when the cutter insert is firmly clamped, forcecomponents occur which force the cutter insert in the direction towardthe axis of rotation D of the tool 101. This means that the side edge133 of the cutter insert 103′ extends at an acute angle relative to thehypothetical center line 143, the distance between the left-hand sideedge 133 and the center line 143 increasing from bottom to top. In sucha case, i.e. if the cutter insert is configured as a parallelogram, theclamping surface 111 can again have two clamping surface regions 139 and141, as is indicated by an interrupted intersection line 145.

In such a case, therefore, there are then two clamping surfaces which,when the cutter insert 103′ is firmly clamped, permit the occurrence offorce components which act against the centrifugal force. It maytherefore be seen that a cutter insert 103′ with the external contoursand a clamping surface 111′ represented in FIG. 9 can be additionallyprovided with a clamping surface 111, as has been described in detailabove.

Even if the cutter insert 103 is not configured as a reversible insert,it is not only possible to configure the clamping surface 111 so that itrises from the left-hand side edge 133 or from the left-hand boundaryedge B toward the right-hand side edge 133′ or toward the right-handboundary edge B′ but it is also possible to provide it with aninclination so that the clamping surface 111 falls away from the rightto the left. In this case also, therefore, the clamping surface 111 isinclined in two directions relative to a hypothetical central plane ofthe cutter insert 103′ extending parallel to the plane of representationin FIG. 9 so that, when a clamping lip 109 acts on the clamping surface111, at least one force component occurs which acts against thecentrifugal force. In addition, at least one force component, which actsagainst the centrifugal force, arises under the action of the clampingforces built up by the clamping shoe 105 in the region of the clampingsurface 111′. Such a configuration of a cutter insert as is shown inFIG. 9 can therefore, in the case of a doubly inclined clamping surface111, offer a particularly high level of safety against displacement ofthe cutter insert 103′ within a tool 101 at high rotational speeds.

What is claimed is:
 1. A cutter insert for a tool for the finishmachining by chip removal of bore surfaces in workpieces, the cutterinsert comprising: at least one obliquely falling clamping surface whichis inclined about a longitudinal axis of the cutter insert and alsoabout a transverse axis of the cutter insert, wherein the clampingsurface, the clamping surface having a substantially triangularconfiguration including a boundary edge which extends substantiallyparallel to the longitudinal axis and to a side edge of the cutterinsert.
 2. The cutter insert as claimed in claim 1, wherein the cutterinsert is configured as a reversible insert and has two clampingsurfaces.
 3. The cutter insert as claimed in claim 1, wherein the lengthof the clamping surface is smaller than that of the cutter insert. 4.The cutter insert as claimed in claim 1, wherein the cutter insertincludes first and second end surfaces which are transverse to thelongitudinal axis and the clamping surface is substantially centered ona cutter face extending between the first and second end surfaces. 5.The cutter insert as claimed in claim 1, wherein the clamping surfaceextends at an acute angle to the axis of rotation of the tool.
 6. A toolfor the finish machining by chip removal of bore surfaces in workpieces,which comprises at least one cutter insert as claimed in claim
 1. 7. Acutter insert for a tool for the finish machining by chip removal ofbore surfaces in workpieces, the cutter insert comprising: a cutterface; and at least one obliquely falling clamping surface inclined belowa plane of the cutter face about a longitudinal axis of the cutterinsert and also about a transverse axis of the cutter insert.
 8. Thecutter insert as claimed in claim 7, wherein the cutter insert isconfigured as a reversible insert and the clamping surface has twoopposed clamping surface regions, each clamping surface region beingoppositely inclined into the cutter face about the longitudinal axis andthe transverse axis, and wherein both clamping surface regions intersectat an intersection line which extends diagonally with respect to thelongitudinal axis.
 9. The cutter insert as claimed in claim 8, whereinthe intersection line between the clamping surface regions extendsapproximately diagonally to the clamping surface.
 10. The cutter insertas claimed in claim 7, wherein the clamping surface is surrounded by aboundary surface along at least one of the sides of the cutter insert.11. The cutter insert as claimed in claim 7, wherein the clampingsurface is provided on the cutter face of the cutter insert.
 12. Acutter insert for a tool for the finish machining by chip removal ofbore surfaces in workpieces, the cutter insert comprising: at least oneobliquely falling clamping surface inclined about a longitudinal axisand about a transverse axis of the cutter insert and arranged in theregion of a longitudinal side of the cutter insert.
 13. A tool for thefinish machining by chip removal of bore surfaces in workpieces whichcomprises at least one cutter insert as claimed in claim 7.